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Thickness Measurement Technology

The Basics

Sample Thickness Measurement

Sensing Technology: Interferometric Probe 

Measurements: Distance and Thickness

How does it work?

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  1. A broadband white-light LED, or xenon lamp, is used to illuminate the source

  2. The light travels via optical fiber from the source via a fiber coupler to the interferometric probe

  3. The interferometric probe consists of a sample arm and a fixed reference arm in a Michelson configuration

  4. The reflectivity of the static mirror is matched to the reflectivity of the sample for maximum interference contrast 

  5. A long pass filter can be added to remove blue light if measuring photoresist

  6. The interfered light is reflected through the optical fiber via the coupler to a collimating lens that illuminates a volume holographic grating to form a spectrum on a linear CCD camera

  7. The CCD camera generates a spectrum (Intensity versus Frequency) at up to 66 kHz

  8. Real-time Fourier Transform of the spectrum (with appropriate bandpass filtering) results in the axial distance or thickness information used to locate the plane of each surface along the measuring distance of the interferometric probe

  9. Mechanical scanning of the sample under the single-point probe results in a high-lateral resolution 4D (X,Y,Z,Thickness) surface topography and thickness point cloud data array

Tel: (704) 893 - 0399

Hours: 9am - 7pm

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